The role of ongoing neuronal activity for baseline and stimulus-induced BOLD signals in the rat hippocampus
The role of ongoing neuronal activity for baseline and stimulus-induced BOLD signals in the rat hippocampus
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DOI：
10.1016/j.neuroimage.2019.116082
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发表时间：
2019-11-15
期刊：
影响因子：
5.7
通讯作者：
Angenstein, Frank
中科院分区：
文献类型：
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作者：
Angenstein, Frank
为了了解正在进行的神经元活动如何影响基线BOLD信号，在连续低频（2或4 Hz）脉冲刺激右侧穿通通路期间，同时记录雄性大鼠右侧海马中的神经元和由此产生的fMRI反应。尽管不断增加的神经元活动，BOLD信号只是短暂增加，在海马，随后返回到初始水平（2 Hz），甚至到一个始终较低的水平（4 Hz）。尽管BOLD信号的最初瞬时增加与颗粒细胞的尖峰增加相一致，但随后BOLD信号的减少与颗粒细胞尖峰活性无关，但与颗粒细胞兴奋性的持续抑制相一致，即，突触后活动减少，群体尖峰潜伏期延长。BOLD信号的下降发生在局部脑血容量（CBV）升高的情况下，因此颗粒细胞兴奋性的降低伴随着高耗氧量。当先前或当前刺激减少基线BOLD信号时，随后的短刺激期仅引起衰减的BOLD反应，即使当颗粒细胞的实际尖峰活动相似时。因此，刺激诱导的BOLD反应的质量关键取决于当前存在的抑制活性，其与基线BOLD信号密切相关。因此，一个有意义的解释刺激诱导的BOLD反应应考虑缓慢发展的变化，基线BOLD信号，因此，基线校正工具应谨慎使用功能磁共振成像数据分析。
To understand how ongoing neuronal activity affects baseline BOLD signals, neuronal and resultant fMRI responses were simultaneously recorded in the right hippocampus of male rats during continuous low-frequency (2 or 4 Hz) pulse stimulation of the right perforant pathway. Despite continuously increased neuronal activity, BOLD signals only transiently increased in the hippocampus and subsequently returned to either the initial level (2 Hz) or even to a consistently lower level (4 Hz). Whereas the initially transient increase in BOLD signals coincided with an increased spiking of granule cells, the subsequent reduction of BOLD signals was independent of granule cell spiking activity but coincided with persistent inhibition of granule cell excitability, i.e., with reduced post-synaptic activity and prolonged population spike latency. The decline in BOLD signals occurred in the presence of an elevated local cerebral blood volume (CBV), thus the reduction of granule cell excitability is attended by high oxygen consumption. When previous or current stimulations lessen baseline BOLD signals, subsequent short stimulation periods only elicited attenuated BOLD responses, even when actual spiking activity of granule cells was similar. Thus, the quality of stimulus-induced BOLD responses critically depends on the current existing inhibitory activity, which closely relates to baseline BOLD signals. Thus, a meaningful interpretation of stimulus-induced BOLD responses should consider slowly developing variations in baseline BOLD signals; therefore, baseline correction tools should be cautiously used for fMRI data analysis.